To solve the outline information of target obscure at low contrast, different surface roughness of target and background causing big different polarization characters of electromagnetic radiation, used polarization imaging technology to detect different polarization radiation with different targets and backgrounds and greatly enhanced target outline. Added rotation polarizer in intensity image system, obtained polarized images of target in different angles under shade, used Stokes parameters to calculate target polarization image, the polarization image of the target under the shadow and the low contrast target is processed. The results show that the target outline information can be greatly increased, the target boundary and texture information increase and the target outline is clearly under shade and is good for recognition under shade and in low contrast.